The present invention relates generally to cordless and wireless data communication for portable computers, and more specifically to such communication that is non-cellular in nature and accomplished via a distributed modem.
Mobile computing has become increasingly important. Many computer users even use their portable computers (i.e., laptop and notebook computers) not only as their main computer, but as their only computer. Portable computers are now available with features that previously were found on only desktop computers, such as compact-disc read-only-memory (CD-ROM) drives, high-resolution color display screens, internal modems, expansion capability (in form of PC Card/PCMCIA Card slots), and in a few instances, integrated printers. With the advent of long-lasting batteries, the portable computer user with few exceptions is completely cordless in using the computer. Nearly everything the user needs is integrated within the portable computer itself.
The significant exception to maintaining a cordless working environment is the necessity of still being tethered by a phone cord when using a modem. While an internal battery frees the computer user from having to plug the computer into a power outlet, an internal modem still forces the computer user to plug the computer into a phone jack in order to communicate. Because computer communications are increasingly important, for example, to stay current through electronic mail and to remain hooked into a company computer network, the inability to remain completely cordless when using a modem with a portable computer is a serious inconvenience.
A limited solution is to attach a cellular phone to the modem. By attaching a cellular phone, the computer user remains completely mobile even when downloading electronic mail or hooking into a network. However, using a cellular phone is disadvantageous in that it is very expensive. Another limited solution is to frequency modulate the audio signal of the internal modem for wireless transmission to a base station; this solution, however, does not provide the user immunity to inevitable drop-outs of the modulated signal that may occur. Because the audio signal emanating from the internal modem is an analog signalxe2x80x94not a digital signalxe2x80x94no error correction can be built into the signal to protect against drop-outs.
Still another limited solution is to transmit serial data wirelessly between the portable computer and a base station in which a complete modem is provided, as is described in U.S. patent application Ser. No. 08/903,070, filed on Jul. 30, 1997, and entitled xe2x80x9cNon-Cellular Cordless/non-wireless Data and Voice Communication for Portable Computers.xe2x80x9d A disadvantage to this solution, however, is that should the user also desire to have non-cordless/non-wireless modem communication, a complete modem is required to be installed into the portable computer as well as into the base station. This is costly and may be cost-prohibitive, because the user is required to purchase two complete modems: one in the base station for wireless communications, and one in the modem for non-wireless communications. For example, a business person traveling with a laptop computer may require a wireless modem when in an airport, and a wired modem when in a hotel.
Therefore, there is a need for a portable computer to remain completely cordless even when using a modem that overcomes the above-described shortcomings and problems. Such a solution should permit a computer user to connect to the Internet, access a company network, download electronic mail, etc., all without being tethered to a phone cord attached to a phone jack. Such a solution should not be cost prohibitive to the computer user, in the way that a cellular phone attached to a computer modem is, or in the way that a complete modem being required in both a computer and a base station is. Such a solution should also protect against inevitable drop-outs of the wireless signal, in the way that modulation of the audio signal of a modem installed on a computer does not.
The above-mentioned shortcomings are addressed by the present invention, which will be understood by reading and studying the following specification. The present invention describes a distributed modem for non-cellular cordless/wireless data communication for portable computers. The modem is distributed among a computer and a base station. In one embodiment, the digital signal processor (DSP) of a modem resides within a PC Card/PCMCIA card for insertion into the computer, while the coder/decoder (CODEC) and data-access arrangement (DAA) of the modem reside within a base station. Radio frequency (RF) transceivers at both the PC Card/PCMCIA card and the base station permit the DSP to wirelessly communicate with the CODEC. Preferably, the DAA attaches to a telephone plug for coupling to a telephone jack of a standard plain-old-telephone service (POTS). The invention, however, is not limited to application in conjunction with a PC Card; it may also be applied to an internal modem, for example.
In the case where the portable computer is running off a battery and therefore is otherwise untethered by cables or wires, the invention provides for completely cordless and cost-effective communication over a modem. The DSP of the modem residing within the PC Card/PCMCIA card inserted into the computer communicates with the CODEC and DAA of the modem at the base station wirelessly via the RF transceivers. Therefore, the computer remains completely cordless. However, because the DAA is still preferably connected to a POTS line through a telephone jack, the cost advantage of connecting through the POTS instead of a cellular network is maintained. The invention eliminates the physical connection between the DSP of the modem and the CODEC of the modem, but maintains the physical connection between the CODEC and DAA of the modem and the phone jack. That is, the invention provides for wireless communications.
Furthermore, to also provide for non-cordless/non-wireless communications without duplicating an entire modem, only the part of the modem distributed to the base station requires duplication at the computer. For example, a PC Card/PCMCIA card according to the invention need only also include a CODEC and a DAA to permit wired communications in addition to wireless communications. While this results in a complete modem at the computer, the base station still does not have a complete modem (viz., the DSP is missing), providing the invention with a cost advantage. Finally, because the signal from the DSP is being transmitted wirelessly in one embodiment, and this signal is a digital signal, error correction can be provided so that inevitable drop-outs of the wireless signal do not occur.
In different embodiments of the invention, computerized systems and hardware cards (such as PC Cards/PCMCIA Cards) of varying scope are described. Still other and further aspects, advantages and embodiments of the present invention will become apparent by reference to the drawings and by reading the following detailed description.